A secure communications unit uses a set of unique numbers, called keys, to encrypt and decrypt messages. These encryption keys must be stored in memory until they are replaced with new keys or are erased. The device responsible for the maintenance of these keys works as a sentry device. The sentry device continuously monitors the environment and erases these keys upon the detection of an illegal, or alarm-triggering, event.
As with many such devices, a battery provides power to the sentry device when normal power is unavailable. During the monitoring process, the power consumed by the sentry device is negligible. However, a great deal of energy is exhausted to erase the keys from the memory when an illegal event is detected.
Prior art sentry devices currently do not check if the keys in memory were already erased and proceed to re-erase keys whenever improper usage or handling is detected. These unnecessary key erases decrease battery life without performing a beneficial task.
In present secure memory devices, the secure memory is erased each time an alarm condition occurs while operating in the standby power mode. This in turn requires a standby power source to supply power to perform the erasure of the secure memory even though secure information had already been erased from the memory device. This method is both costly and inefficient.
Accordingly, a need exists for a method that erases memory in a device only when absolutely required to maintain the integrity and security of the device.